This application is a national stage application, according to Chapter II of the Patent Cooperation Treaty.
The invention relates to a method for producing a ring traveler for ring spinning or ring twisting machines and to a ring traveler as claimed in claims 1 and 7 respectively.
Ring travelers of ring spinning and ring twisting machines are moved at a high rotational speed (30 m/s to 50 m/s) on rings of the corresponding ring spinning or ring twisting machines. Both the contact surface between ring traveler and ring and the contact surface between ring traveler and thread are subjected to a high degree of wear. To increase production, however, increasingly higher running speeds of the ring travelers are required. By longer service lives being achieved, the costs are at the same time to be lowered.
It has been possible, in recent years, to improve the running and operating properties of ring travelers markedly by these being coated with appropriate materials. However, it has not been possible hitherto to improve the wear resistance at the thread passage.
U.S. Pat. No. 4,677,817 discloses a ring traveler having a ceramic layer which gives the ring traveler greater hardness and improved heat and corrosion resistance. This known ring traveler has markedly reduced operating costs due to the improved running and operating properties. However, the relatively high outlay in terms of production has an adverse influence on costing.
The object of the present invention is, therefore, to provide a ring traveler for ring spinning or ring twisting machines, which, on the one hand, has further-improved running and operating properties and, on the other hand, can be produced at a reduced outlay. A method for producing this ring traveler is also to be specified.
This object is achieved by means of a method and a ring traveler which have the features specified in claim 1 and claim 7 respectively.
A ring traveler according to the invention has a noncoated core which consists of iron material and which has an, if appropriate, multipart nitrided edge layer at least in the region of the running surfaces with which said core slides on a ring of a ring spinning or ring twisting machine or in which the thread is guided.
Instead of a layer, for example a ceramic or phosphate layer, being applied to the core and, if appropriate, being remachined, at considerable outlay, said core is subjected, at least partially, to a nitriding treatment, during which heat energy and a nitriding agent as active medium are supplied to the core.
Embrittlement and a considerable reduction in the elasticity of the treated material are known to occur during nitriding treatment. By the composition of the nitriding agent being controlled according to the invention and by an appropriately selected treatment time, the elasticity of the ring traveler, which is necessary so that the latter can be attached, free of deformation, onto spinning rings, can be maintained.
The core is heated to a temperature in the range of 450xc2x0 C.-600xc2x0 C., preferably to a temperature close to 550xc2x0 C., and is maintained in said temperature range for 3-60 hours, preferably for about 24 hours. The nitriding agent may be supplied in the form of a gas, liquid or plasma preferably consisting of NH3 and N2 components. Regions in which nitriding treatment is not to take place are, for example, covered.
The nitrided edge layer of the ring traveler core consists of a connecting layer without an additional diffusion layer, of a connecting layer with an additional diffusion layer lying radially on the inside or only of a diffusion layer. The connecting layer has preferably a thickness of 0.1 xcexcm-30 xcexcm and the diffusion layer a thickness of 1 xcexcm-2000 xcexcm.
Preferably, the active medium has, in addition to the nitrogen components, sulfur components and/or carbon components. By sulfur components and/or carbon components being admixed, the coefficient of friction can be reduced. At the same time, the thicknesses of the connecting layer and of the diffusion layer can be coordinated, as required.
When small thicknesses of the connecting layer are selected, only slight variations in the roughness of the core surface are obtained.
In preferred refinements of the invention, the surface of the ring traveler is additionally polished before and/or after the nitriding treatment. Ring travelers exposed to high chemical stress are preferably reoxidized.
In so far as a core made from a heat-treated steel is used, only negligibly small changes in dimension occur during the nitriding treatment.
The ring travelers according to the invention have substantially improved operating properties, in particular an increased traveler service life and increased indentation resistance at the thread passage. The functionally very important indentation resistance in the thread passage with a mechanical and/or chemical load was improved by 50%-200%, thus resulting in an improvement in the quality of the processed yarn. Furthermore, by virtue of the increased chemical resistance, yarn contaminations due to corrosion products which previously occurred during the processing of revived and chlorine-containing fibers are avoided. Moreover, because of the good sliding properties, no or only slight fiber lubrication is required.
Furthermore, the ring travelers can be produced at lower outlay and adapted to individual requirements which may possibly arise.
Ring travelers according to the invention may be used both in spinning mills and in twisting mills. Their good running properties, such as, for example, good sliding and low wear, are implemented particularly advantageously in cooperation with steel rings, but they may also be used on other rings, such as, for example, on sintered, burnished or coated rings.